Acta Phys. -Chim. Sin. ›› 2015, Vol. 31 ›› Issue (9): 1810-1814.doi: 10.3866/PKU.WHXB201507203

• PHYSICAL CHEMISTRY OF MATERIALS • Previous Articles     Next Articles

Simulation of the Immobilization of Pu in the Gd2Zr2O7 Matrix by Investigating the Thermophysical Properties of (Gd1-xCex)2Zr2O7+x

Xiang-Lai. XIA1,2,Lin-Yan. LI2(),Fang. GUO1(),Wei. SU3,Yan. LIU3,Xiao-Mou. CHEN3,She-Qi. PAN3   

  1. 1 College of Chemistry, Liaoning University, Shenyang 110036, P. R. China
    2 Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, P. R. China
    3 China Academy of Engineering Physics, Mianyang 621900, Sichuan Province, P. R. China
  • Received:2015-03-26 Published:2015-09-06
  • Supported by:
    NSAF(11176014);National Natural Science Foundation of China(21471088)

Abstract:

Polycrystalline samples of (Gd1-xCex)2Zr2O7+x (0 ≤ x ≤ 0.7) were synthesized by solid-state reaction using NaF as a flux at 1000 ℃ to simulate Pu-immobilization in the Gd2Zr2O7 matrix. Phase transformation and variation of the thermal expansion coefficients (TECs) and thermal conductivities (TCs) of the samples with temperature and composition were investigated. Powder X-ray diffraction (XRD) patterns show that pure Gd2Zr2O7 has a weakly ordered pyrochlore structure, whereas Ce-containing samples (i.e., the Pu-simulated solidified samples) exhibit a defect fluorite structure even if x is as low as 0.1. When x reaches 0.7, the XRD peaks of these samples widen. In the Ce 3d X-ray photoelectron spectrum (XPS) of (Gd1-xCex)2Zr2O7+x there are six peaks located at binding energies of 881.7, 888.1, 897.8, 900.4, 907.1, and 916.1 eV, which are almost the same as the peaks of CeO2. The Ce 3d XPS reveals that the Ce species in (Gd1-xCex)2Zr2O7+x are tetravalent. The TECs of (Gd1-xCex)2Zr2O7+x (0 ≤ x ≤ 0.7) generally increase with increasing temperature. At the same temperature, the TECs and TCs exhibit the same variation trend with the composition of the simulated solidified forms: they decrease from x = 0 to 0.1 and then linearly increase from x = 0.1 to 0.7.

Key words: Immobilization of nuclear waste, Pyrochlore structure, Defect fluorite structure, Thermal expansion coefficient, Thermal conductivity

MSC2000: 

  • O642